php number length should be 4 add zeros code example
Example 1: prepend 0 to number php
str_pad($month, 2, '0', STR_PAD_LEFT);
Example 2: php pad leading zeros
str_pad($value, 8, '0', STR_PAD_LEFT);
str_pad($month, 2, '0', STR_PAD_LEFT);
str_pad($value, 8, '0', STR_PAD_LEFT);